Antifogging agent and bactericide for photographic emulsions



Patented July 28, 1959 ANTIFOGGING AGENT AND BAC'I E RICIDE FOR PHOTOGRAPHIC EMULSIONS Fritz Derscli and Millet R. De Angelus, Binghamton, N.Y., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation 'of Delaware N Drawing. Application December 30, 1957 Serial No. 705,729

6 Claims. (Cl. 96-66) The present invention relates to the use of anti-fogging and stabilizing agents for photographic silver halide emulsions and, more particularly, to the employment of carboxy-alkyl-pentahalo-benzenethio-ethers, their salts and esters for such purpose.

It is recognized that light-sensitive emulsions such as gelatino-silver halide emulsions have a tendency to fog. The fog may be caused in a number of ways as, for example, by excessive ripening of the emulsion, by storage of the light-sensitive element at elevated temperatures and humidity or by prolonged development of the exposed emulsion.

We have now found that carboxyalkyl-pentahalo-benzenethio-ethers, their salts and esters are excellent stabilizers and antifog'gants for silver halide emulsions having the ability to maintain the sensitivity and fog at or close to initial optimum values under keeping conditions of high temperature and humidity. Said compounds also have the characteristic of inhibiting bacteria growth in photographic gelatin emulsions.

The use of such compounds to inhibit fog and to stabilize silver halide emulsions either by location of the same in the emulsion, in layers adjacent to the emulsion or in processing baths for the emulsion constitutes the purposes and objects of the present invention.

The carboxyalkyl-pentahalo-benzenethio-ethers, the use of which is contemplated herein, may be represented by the following formula:

wherein R is hydrogen, an aliphatic radical such as alkyl, i.e., methyl, ethyl, propyl, butyl, amyl and the like; hydroxyalkyl, i.e., hydroxymethyl, hydroxyethyl and the like; carboxyalkyl, i.e., carboxymethyl, carboxyethyl and the like; aryl such as phenyl, toluyl, naphthyl, carboxyphenyl, sulfophenyl and the like; aralkyl such as benzyl or a salt-forming group, i.e., sodium, potassium, ammonium, silver orthe like; X is halogen, i.e., chloro, bromo or the l ike; and n is a whole number of from 1 to 3.

Examples of compounds within the ambit of such formula which we have found to be efiective are:

l. Carboxymethyl-pentachloro-benzenethio-ether 2. The methyl, ethyl or phenyl ester of carboxymethylpentachloro-benzenethio-ether 3. Carboxymethyl-pentabromo-benzenethio-ether and its sodium, potassium and silver salt 4. Carboxyethyl-pentachloro-benzenethio-ether and the methyl, ethyl or phenyl esters thereof 5. Carboxyethyl-pentabromo-benzenethio-ether 6. Carboxypropyl-pentachloro-benzenethio-ether 7. Carboxypropyl-pentabromo-benzenethio-ether and the methyl, ethyl or butyl esters thereof ing the desired cation such as potassium carbonate, so-

dium carbonate, ammonium carbonate, silver nitrate or the like.

If the esters are desired, they may be produced in the conventional manner by refluxing the free acid with the desired alcohol such as methyl alcohol, ethyl alcohol, butyl alcohol or with a phenol in the presence of hydrochloric acid.

Beneficial effects and fog reduction are obtained when aqueous solutions of the aforementioned compounds are incorporated in the silver halide emulsions as ripening finals or as coating finals. Ripening finals are added during the ripening or the sensitivity increasing stage of the emulsion making process. Such additions may be made before, during or after the decomposition of the soluble silver salt such as silver nitrate by means of a soluble halide such as potassium bromide, sodium chloride or the like in the presence of a colloidal carrier such as gelatin, PVA, solubilized casein or albumen.

Coating finals are added to the emulsion just prior to coating on a suitable support such as glass, paper or film at a time when the emulsion has nearly obtained its maximum sensitivity.

When used as ripening finals the antifoggants are best employed in a concentration of /2 to 5 mg. per .4 mol of silver halide and when used as coating finals in a concentration of .5 to 300 mg. per .4 molof silver halide. The concentration used depends on the type of emulsion employed and it is advisable to determine the optimum concentration from case to case. In some instances, it is advantageous to apply the antifoggant and stabilizers in layers adjacent to the emulsion, that is, in a separate undercoating layer or in the anti-abrasion gelatin surface. In other instances, the desired result may be procured by addition of the antifoggant and stabilizer to one or several processing baths such as developer, fixer or the like.

The aforesaid antifoggants and stabilizers may be utilized in connection with any type of photographic emulsion, e.g., non-sensitized, orthochromatic, panchromatic, X-ray emulsions, paper emulsions, color emulsions or the like. They may be employed in combination with other known antifoggants and stabilizers, reductionand metaland noble metal sensitizers, or in combination with hydroxypolyethenoxy derivatives, i.e., those obtained by reacting ethylene oxide with an alcohol, phenol, amine or the like (see US. Patent 1,970,578).

The invention is illustrated by the following examples, but it is to be understood that the invention is not restricted thereto.

Example I A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was prepared in a conventional manner and brought up to its maximum light sensitivity. It was then readied for coating, finals were added such as sensitizing dyes, stabilizers and hardeningagents. A 1% solution of carboxymethyl-pentachloro-benzenethioether was added to the emulsion as an antifoggant. The

emulsion samples contained about .4 mol of silver halide.

The so prepared emulsion samples were coated on a suit able cellulose ester base and dried. Samples of these film coatings were then exposed in a Type 1113 Sensitometer and The carboxymethyl-pentachloro-benzenethio-ether was prepared as follows:

11.6 grams of pentachloro-benzenethiol, 6.99 grams of bromoacetic acid and 125 mls. of 1-Nsodium hydroxide solution were heated under reflux for 2 /2 hours. After cooling, the reaction mixture was acidified with dilute hydrochloric acid, using Congo red paper as an indicator. A white solid was collected, dissolved in a minimum of ethanol and treated with Norite (charcoal). Crystallization was effected by the addition of Water. The product was recrystallized from ethanol-dimethyl formamide and dried.

The product had the following formula:

Cl C1 Example 11 The procedure was the same as in Example I excepting that the carboxymethyl-pentachloro-benzenethio-ether was replaced by an equivalent quantity of the methyl ester thereof. ample I were secured in this instance.

The methyl ester was prepared by refluxing 1 mol. of carboxymethyl-pentachloro-benzenethio-ether with a slight excess of methyl alcohol in the presence of hydrochloric acid.

Example III The procedure was the same as in Example I excepting that the carboxymethyl-pentachloro-benzenethioether was replaced by an equivalent quantity of carboxyethyl-pentachloro-benzenethio-ether. The results were similar to those of Example I.

The carboxyethylpentachlorobenzenethioether was produced in the same manner as the carboxymethyl-pentachlorobenzenethio-ether excepting that the bro-moacetic acid was replaced by an equivalent quantity of bromopropionic acid.

Example IV A silver halide emulsion in gelatin containing 64% of exhibited a relative speed of 100 and a fog of 0.12 compared with a type coating of the same emulsion having an undercoating similar to that described above, but lacking the antifoggant and having a speed of 100 and a fog of 0.20.

Example V The procedure was the same as in Example IV excepting that the carboxymethyl-pentachloro-benzenethio-ether was replaced by an equivalent quantity of carboxypropylpentachloro-benzenethio-ether. The results were similar to those obtained in Example IV.

Example VI The procedure was the same as in Example IV excepting that the carboxymethyl-pentachloro-benzenethio-ether was replaced by an equivalent quantity of carboxymethylpentabromo-benZenethio-ether. The results were substantially the same as those of Example IV.

The carboxymethyl-pentabromo-benzenethio-ether was prepared in the same manner'as carboxymethyl-pentachloro-benzenethio-ether excepting that the pentach1oro benzenethiol was replaced by an equivalent quantity of pentabromo-benzenethiol.

Example VII Exposed samples of a photographic film were developed for twelve minutes at 65 F. in a standard metol-hydroquinone developer. Two tests were made, one with the normal developing solution and one with a developer containing 60 mgs. of carboxyinethyl-pentachloro benzenethio-ether per one liter of developer. Sensitometric strips, developed in the normal developer (control) for twelve minutes, showed a fog of .30, whereas those strips which were developed in the developer containing the antifog- Cir Results similar to those obtained in Exsilver bromide and 36% of silver chloride and also con gant had a fog of .20.

Various modifications of the invention will occur to persons skilled in the art. Thus, it is understood that in lieu of using the particular antifoggants of the examples, any of the antifoggants listed in the application may be employed with equivalent results. We therefore, do not intend to be limited in the patent granted except as necessitated by the appended claims.

We claim:

1. A light-sensitive photographic material comprising a base and a light-sensitive silver halide emulsion, said light-sensitive material containing as an antifoggant a compound of the following constitution:

wherein R is selected from the class consisting of hydrogen, an aliphatic radical, aryl, aralkyl and a cation; X is halogen and n is a whole number of from 1 to 3.

2. The article as defined in claim 1 wherein the antifoggant is located in the silver halide emulsion.

3. The article as defined in claim 1 wherein the antifoggant is located in a layer adjacent to said silver halide emulsion layer.

4. A light-sensitive photographic material comprising a base with a light-sensitive silver halide emulsion thereon, said emulsion containing as an antifoggant the compound carboxymethyl-pentachloro-benzenethio-ether of the following formula:

5 5. The process of minimizing and preventing fog in light-sensitive silver halide materials comprising a base having a light-sensitive silver halide emulsion thereon, which comprises exposing said emulsion to light and developing the same in the presence of an antifoggant and stabilizer of the following structural formula:

in which R is selected from the class consisting of hydrogen, an aliphatic radical, aryl, aralkyl and a cation; X is halogen and n is a whole number of from 1 to 3.

6. The process as defined in claim 5 wherein the antifoggant is carboxymethyl-pentachloro-benzenethio ether of the following formula:

S-CHz-OOOH No references cited. 

1. A LIGHT-SENSITIVE PHOTOGRAPHIC MATERIAL COMPRISING A BASE AND A LIGHT-SENSITIVE SILVER HALIDE EMULSION, SAID LIGHT-SENSITIVE MATERIAL CONTAINING AS AN ANTIFOGGANT A COMPOUND OF THE FOLLOWING CONSTITUTION: 